Field of the Invention
The present invention relates generally to a method for forming an aluminum nitride-based film on a substrate by plasma-enhanced atomic layer deposition (PEALD).
Related Art
Copper (Cu) has been used as a primary wiring material in multilevel interconnection of silicon devices. Since Cu easily diffuses to a transistor layer, an insulating layer, or the like, Ta/TaN or the like is used as a barrier metal layer facing the side and bottom of Cu wiring, and SiN, SiCN, or the like is typically used as a diffusion barrier layer and/or etch stop layer deposited on top of the Cu wiring.
In speed enhancement and energy savings of silicon devices, it is necessary to lower the effective dielectric constant of the devices themselves, and conventional diffusion barrier layers and etch step layers are not satisfactory. There are methods of lowering the effective dielectric constant. For example, by making the diffusion barrier layers and the etch stop layers thin, the effective dielectric constants of devices may be lowered. However, when the thickness of a film is in an extremely low range of 3 to 5 nm, the tunnel effect of electrons becomes more significant, and accordingly, the leakage current of the layers increases.
Aluminum nitride (AlN) is expected to replace SiCN used as a diffusion barrier layer and an etch stop layer. The present inventors have conducted research on leakage current improvement by an ultra thin film of AlN.
Any discussion of problems and solutions in relation to the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made.